A comparator module is used to store a reflection time from the ultrasonic receiver. Then, the obstacle’s distance is calculated from the time. If the object distance is less
than 130 cm, the motor is started and it starts to vibrate. The vibration frequency will increase as the obstacle distance decreases. The device’s battery voltage is monitored
by the microcontroller’s Analog-to-Digital Converter (ADC) Module. If the voltage reaches a lower level or less than 3.4 volts, an alerting sound from the device’s speaker will warn the user to recharge the battery. For security reasons, the device will shut itself down when the voltage reaches a critical level or less than 3.0 volts.